cmake使用及如何编写CMakeLists.txt文件

1.cmake 简介

CMake是一个跨平台的安装(编译)工具,可以用简单的语句来描述所有平台的安装(编译过程)。他能够输出各种各样的makefile或者project文件,能测试编译器所支持的C++特性,类似UNIX下的automake。

2.CMake 操作流程

CMake的所有的语句都写在一个叫:CMakeLists.txt的文件中。当CMakeLists.txt文件确定后,可以用ccmake命令对相关的变量值进行配置。这个命令必须指向CMakeLists.txt所在的目录。配置完成之后,应用cmake命令生成相应的makefile（在Unix like系统下）或者 project文件（指定用window下的相应编程工具编译时）。

其基本操作流程为：

$ ccmake directory
$ cmake directory
$ make

其中directory为CMakeList.txt所在目录；

第一条语句用于配置编译选项，如VTK_DIR目录，一般这一步不需要配置，直接执行第二条语句即可，但当出现错误时，这里就需要认为配置了，这一步才真正派上用场；
第二条命令用于根据CMakeLists.txt生成Makefile文件；
第三条命令用于执行Makefile文件，编译程序，生成可执行文件；

CMake的执行就是这么简单，其难点在于如何编写CMakeLists.txt文件

3.如何编写CMakeLists.txt文件

3.1 开头通用模块

make版本要求

cmake_minimum_required( VERSION 2.8 )

工程文件名-可任取

project(project)

编译模式

# 设置为 Release 模式
SET(CMAKE_BUILD_TYPE Release)

# 设置为 debug 模式
SET(CMAKE_BUILD_TYPE debug)

# 打印设置的编译模型信息
MESSAGE("Build type: " ${CMAKE_BUILD_TYPE})

检查C++版本

# Check C++11 or C++0x support
include(CheckCXXCompilerFlag)
CHECK_CXX_COMPILER_FLAG("-std=c++11" COMPILER_SUPPORTS_CXX11)
CHECK_CXX_COMPILER_FLAG("-std=c++0x" COMPILER_SUPPORTS_CXX0X)
if(COMPILER_SUPPORTS_CXX11)
   set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11")
   add_definitions(-DCOMPILEDWITHC11)
   message(STATUS "Using flag -std=c++11.")
elseif(COMPILER_SUPPORTS_CXX0X)
   set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++0x")
   add_definitions(-DCOMPILEDWITHC0X)
   message(STATUS "Using flag -std=c++0x.")
else()
   message(FATAL_ERROR "The compiler ${CMAKE_CXX_COMPILER} has no C++11 support. Please use a different C++ compiler.")
endif()

3.2 项目文件配置模块

如果仅包含OpenCV库时
- 备注：这里的OpenCV包含目录为含有OpenCVConfig.cmake的路径。

set(OpenCV_DIR "/usr/local/include/opencv3.2.0/share/OpenCV")
find_package(OpenCV REQUIRED)

include_directories( ${OpenCV_INCLUDE_DIRS} )

生成可执行文件

ADD_EXECUTABLE(  目标文件（可执行文件）   依赖文件（.cpp）)

add_executable(${PROJECT_NAME} src/loop_closure.cpp )
target_link_libraries(${PROJECT_NAME} ${OpenCV_LIBS})

包含第三库的头文件

#设置.h文件对应的路径
set( DBoW2_INCLUDE_DIRS ${PROJECT_SOURCE_DIR}/ThirdParty/DBow-master/include/)

#包含.h文件路径
include_directories( ${OpenCV_INCLUDE_DIRS}
         ${DBoW2_INCLUDE_DIRS} ${DBoW2_INCLUDE_DIRS}/DBoW2/)

包含第三方库的cpp文件

set(DBoW2_SRCS "${PROJECT_SOURCE_DIR}/ThirdParty/DBow-master/src")

#生成可执行文件 -- 使用空格分割cpp文件路径
add_executable(${PROJECT_NAME} src/loop_closure.cpp src/run_main.cpp ${DBoW2_SRCS}/BowVector.cpp ${DBoW2_SRCS}/FBrief.cpp ${DBoW2_SRCS}/FeatureVector.cpp ${DBoW2_SRCS}/FORB.cpp ${DBoW2_SRCS}/FSurf64.cpp ${DBoW2_SRCS}/QueryResults.cpp ${DBoW2_SRCS}/ScoringObject.cpp)

3.3 一个简单的CMakeLists.txt文件demo

cmake_minimum_required( VERSION 2.8 )
project( loop_closure )

#set(CMAKE_BUILD_TYPE  Debug)
IF(NOT CMAKE_BUILD_TYPE)
  SET(CMAKE_BUILD_TYPE Release)
ENDIF()

MESSAGE("Build type: " ${CMAKE_BUILD_TYPE})

# Check C++11 or C++0x support
include(CheckCXXCompilerFlag)
CHECK_CXX_COMPILER_FLAG("-std=c++11" COMPILER_SUPPORTS_CXX11)
CHECK_CXX_COMPILER_FLAG("-std=c++0x" COMPILER_SUPPORTS_CXX0X)
if(COMPILER_SUPPORTS_CXX11)
   set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11")
   add_definitions(-DCOMPILEDWITHC11)
   message(STATUS "Using flag -std=c++11.")
elseif(COMPILER_SUPPORTS_CXX0X)
   set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++0x")
   add_definitions(-DCOMPILEDWITHC0X)
   message(STATUS "Using flag -std=c++0x.")
else()
   message(FATAL_ERROR "The compiler ${CMAKE_CXX_COMPILER} has no C++11 support. Please use a different C++ compiler.")
endif()

#opencv
#set(OpenCV_DIR "/usr/local/include/opencv3.2.0/share/OpenCV")
set(OpenCV_DIR "/opt/ros/kinetic/share/OpenCV-3.3.1-dev")

find_package(OpenCV REQUIRED)

set( DBoW3_INCLUDE_DIRS "/usr/local/include")

set( DBoW2_INCLUDE_DIRS ${PROJECT_SOURCE_DIR}/ThirdParty/DBow-master/include/)
message(${DBoW2_INCLUDE_DIRS})

#important
#file(GLOB DBoW2_SRCS ${PROJECT_SOURCE_DIR}/ThirdParty/DBow-master/src/*.cpp)
#message(${DBoW2_SRCS})

set(DBoW2_SRCS "${PROJECT_SOURCE_DIR}/ThirdParty/DBow-master/src")
message(${DBoW2_SRCS})

find_package(DLib QUIET
        PATHS ${DEPENDENCY_INSTALL_DIR})
if(${DLib_FOUND})
   message("DLib library fo  NDENCY_DIR}
              GIT_REPOSITORY http://github.com/dorian3d/DLib
              GIT_TAG master
              INSTALL_DIR ${DEPENDENCY_INSTALL_DIR}
              CMAKE_ARGS -DCMAKE_INSTALL_PREFIX=<INSTALL_DIR>)
      add_custom_target(Dependencies ${CMAKE_COMMAND} ${CMAKE_SOURCE_DIR} DEPENDS DLib)
   else()
      message(SEND_ERROR "Please, activate DOWNLOAD_DLib_dependency option or download manually")
   endif(${DOWNLOAD_DLib_dependency})
endif(${DLib_FOUND})


include_directories( ${OpenCV_INCLUDE_DIRS}
        ${DBoW3_INCLUDE_DIRS} ${DBoW2_INCLUDE_DIRS} ${DBoW2_INCLUDE_DIRS}/DBoW2/)

message("DBoW3_INCLUDE_DIRS ${DBoW3_INCLUDE_DIRS}")
message("DBoW2_INCLUDE_DIRS ${DBoW2_INCLUDE_DIRS}")

message("opencv ${OpenCV_VERSION}")

# dbow3
# dbow3 is a simple lib so I assume you installed it in default directory
set( DBoW3_LIBS "/usr/local/lib/libDBoW3.a")

add_executable(${PROJECT_NAME} src/loop_closure.cpp  src/run_main.cpp
        ${DBoW2_SRCS}/BowVector.cpp ${DBoW2_SRCS}/FBrief.cpp ${DBoW2_SRCS}/FeatureVector.cpp
        ${DBoW2_SRCS}/FORB.cpp ${DBoW2_SRCS}/FSurf64.cpp ${DBoW2_SRCS}/QueryResults.cpp ${DBoW2_SRCS}/ScoringObject.cpp
        )
message(${DBoW2_SRCS}/BowVector.cpp)

target_link_libraries(${PROJECT_NAME}
${OpenCV_LIBS}

${DLib_LIBS}
${DBoW3_LIBS}
)